I want to use My Cloud Home for my main data storage and remove all data from my iMac Hard Drive.
Will I be able to backup the My Cloud Home to a Seagate External Drive?
Can I also backup some files to a remote Cloud provider using this setup? i.e.Dropbox
First, see the dedicated subforum for the My Cloud Home. This subforum (My Cloud) is a different device and has different features/options than the My Cloud Home.
Second, if you haven’t done so already, read through the My Cloud Home User Manual to gain an understanding of that devices options, features and possible limitations with respect to what you are seeking to do with your iMac.